Magnesium base alloy



Patented Mar. 4, 1941 PATENT OFFICE MAGNESIUM BASE ALLOY John C.McDonald, Midland, Mich, assignor to The Dow Chemical Company, Midland,Mich, a corporation of Michigan No Drawing. Application March 30, 1940,

Serial No. 327,034

30mins. (01. 75-103 This invention relates to magnesium base alloys andmore particularly concerns an alloy of this nature having an excellentdegree of formability associated with other desirable physical 5properties such as high tensile and yield strengths.

Magnesium alloys are being widely used in the various structural andmechanical arts where a light weight metal is highly desirable, such as10 for use in making castings, forgings, and the like. However, the useof these alloys in the rolled. form to make sheet metal articlesrequiring forming operations, such as bending, drawing and the like, hasnot progressed as rapidly due to the 15 -fact that in general alloys ofgood formability permitting relatively sharp bends to be made withoutthe articles developing external cracks usually have inferior strengthcharacteristics.

It is accordingly the principal object of the in- 20 vention to providea magnesium base alloy which can be made into rolled sheet or the likepossess ing a suflicient degree of ductility or formability to besharply bent, drawn, or otherwise shaped while having good tensile-andyield strengths.

is obtained when the alloy contains from 1 to 5 percent of zinc, from 2to. 8 per cent of thallium, and from 0.05 to 0.4 per cent of calcium.The specific proportion of each alloying metal and the total amount ofthe alloyin metals to be 5 .added depends upon the use for which thealloy is intended. For example, where excellent ductility or formabilityassociated with good yield and tensile strengths is of principalimportance, the alloy should preferably contain from 0.5 to 10 1.5 percent of zinc, 2 to '7 per cent of thallium, and from 0.05 to 0.4 percent of calcium. However, in those instances where exceptionally highyield and tensile strengths .are more important than formabilitycharacteristics the alloy may contain increased amounts of thallium andzinc.

The following table lists some of the properties of rolled'sheet metalmade from my new quaternary alloy and compares these properties withthose of rolled sheet made from related ternar alloys. A comparison ofthe properties listed illustrates the improvement in the forma-' bilityand strength characteristics of the new alloy over that of theclosely'related ternary alloys.-

Other objects and advantages will be apparent In the table the per centelongation is to be reas the description of theinvention proceeds.garded as a measure of the ductility or forma- My invention resides inthe discovery that a bility of the specimen.

Table 30 zg ggggf t Annealed Cold rolled Yield .Tcnsile Percent YieldTensile Zn T] Ca Strength strength elongation strength strength 35mlbs./sq.1n. inlbs./sq.m. mZinches inlbsJsq. in. inlbsJsq. in.

a magnesium base alloy composed of from 0.3 to 8 The properties hsted 1nthe above table under per cent of zinc, from 1 to 20 per cent ofthallium, the section headed by the term annealed" were and from 0.01 to1 per cent of calcium, the balobtained by first rolling the alloys at atemperaance being substantially all magnesium, 'is enture' of from 400to 550 F. and thereafter an,-

dowed with .the afore-mentioned properties. nealing them at varioustemperatures, in the While the properties of excellent iormability ortemperature range from 400 to 800 F. .The ductility associated with hightensile and yield properties selected for the table were those of thestrengths are manifest over the entire range of annealed specimens whichexhibited the maxithe composition indicated, I have found that in mumelongation. Properties listed in the above general the preferredcombination of properties 55 table under the section "cold rolled" wereobtained by subjecting specimens of the alloy which had been hot rolledat a temperature of from 400 to 550 F. to additional rolling in the cold7 state in order'to improve their strength charac teristics. Theproperties selected for the table were of the cold rolled specimenswhich showed the greatest tensile and yield strengths while having atleast 1 per cent elongation in 2 inches.

By comparison of the properties listed in the above table, it will beobserved that the combined properties of my new quaternary alloy aresuperior to those of closely related ternary alloys having similarpercentages of alloying ingredients. For .example, it will be noted thatthe alloys containing the lower percentages of alloying ingredients havean exceptionally high elongation or formability coupled with superiorstrength characteristics in both the annealed and cold rolled state. Inthe higher percentages of alloying ingredients the formability orductility is fairly good, while the strength characteristics show anexceptionally high degree of improvement. Similar improvement will benoted I throughout the range of alloying ingredients in-- dicated.

While the new alloy is most useful in the wrought form, such as sheets,due to its formability characteristics, it may also be suitably used inmaking castings, forgings, extruded forms and the like. ,It is furtherpointed out that my new alloy is amenable to solution and precipitationheat treatments, which, accordingly, modify its properties.

The new alloy may be compounded in any of v the ways known in the art,such as by adding the much stirring or agitation in order to guardagainst loss of some of the calcium into the flux.

I claim:

1. A magnesium base alloy containing from 0.3 to 8'per cent of zinc,from 1 to 20 per cent of thallium, and from 0.01 to 1 per cent ofcalcium, the balance being magnesium.

' 2. A magnesium base alloy containing from 0.5 to 1.5 per cent of zinc,from 3 to 7 per cent thallium, and from 0.05 to 0.4 per cent of calcium,the 25 balance being magnesium.

3. A magnesium base alloy containing from 4 to 6 per cent of zinc, from3 to '7 per cent of thallium, and from 0.05 to 0.4 per cent of calcium,the balance being magnesium.

J C. MCDONALD.

